Toxicity of silicon compounds in semiconductor industries

The toxicities of silane (SiH₄), tetraethoxysilane (Si(OC₂H₅)₄, TEOS) and dichlorosilane (SiH₂Cl₂, DCS) were reviewed in order to compare the toxicological properties of silicon compounds used in the semiconductor industry. Silane and TEOS showed similar toxicities, characterized by nephrotoxicity. Mice subjected to silane (2500, 5000 and 10000 ppm) or TEOS (1000 ppm) acute exposure developed acute tubular necrosis. Tubulo- interstitial nephritis was seen in mice which were subjected to an acute inhalation study and survived 2 wk of the observation period or those subjected to subacute inhalation studies of TEOS (100 and 200 ppm for 2 or 4 wk). Silane and TEOS, however, differed in the concentration at which they showed signs of toxicity. This may be due to their solubility in water and other metabolic factors, but their metabolic pathways have not yet been elucidated. TEOS injured nasal mucosa (1000 ppm for 2 h or more and 50, 100 and 200 ppm for 2 or 4 wk). It was observed at a lower concentration than nephrotoxicity in the 50 and 100 ppm subacute inhalation study. On the other hand, silane caused nasal mucosal lesions only at 5000 or 10000 ppm for acute inhalation, and those of subacute inhalation were mild (1000 ppm for 2 or 4 wk). DCS showed another type of adverse effect. It was an irritant and/or a corrosive agent to the respiratory tract in the acute (64 ppm for 1,2, 4 or 8 h) and subacute (32 ppm for 2 or 4 wk) inhalation study. The fate of DCS in air was also studied and it was shown to form small particles including silicon and chlorine (CI) atoms. CI seems to play an important role in the toxicity of DCS.